Backport read_quad optimization

[Gozala]

In the rust implementation I have optimized code such that we do not have to read out leaves only to combine pairs into nodes afterwards, which avoids bunch of memory copying

https://github.com/web3-storage/fr32-sha2-256-trunc254-padded-binary-tree-multihash/blob/98fe584ae5ae2c3790ec72c530aff5b36e2b1b92/src/hasher.rs#L143-L179

It would be a good idea to backport this logic here